Safe Mode – If your device hang, freezes randomly, restarts, become slow over time, battery drain so quickly and any other issue then you can boot your device into the safe mode. In this mode the OS temporally turns off all user-installed apps.

Developer options – give you access to ADB settings, USB debugging, and various monitoring tools for your device. It’s also the one of the first steps to rooting your device.

Screenshot – If you want to shar your home screen with friends

Enter the code from the phone dialer app:

*#06# – IMEI number

*#1234# – firmware version

*#0228# – battery info

Use this code *#0*# to enter the phone into the test menu. From this menu you can run tests for vibration, RGB colors, touch-screen, vibration, loudspeaker output, camera, sensor check and so on.